The need to fold and unfold the rotor blades of a helicopter with respect to the helicopter fuselage and a system for doing so are well established as evidenced by U.S. Pat. Nos. 3,153,455; 3,187,818; 3,247,907 and 3,369,610.
New generations of helicopters with their innovations rotor head designs resulting in higher speeds and greater rotor head loads require ever more compact blade folding systems. The present invention represents such a system. For example, it may replace the system disclosed in U.S. patent application Ser. No. 429,365, now U.S. Pat. No. 4,543,040, assigned to the assignee of the present invention. The system which may be replaced is shown in FIG. 1. In its essential parts the lag damper and blade folding mechanism 10 includes an elastomeric lag damper 12, a fold motor and gear box 14 and associated linkages including a bellcrank 16 fastened at the lead-lag hinge 18 to the rotor blade 20. The fold motor and gear box 14 has a rod 22 extending therefrom which engages a bellcrank 24 which in turn is connected to the bellcrank 16 by a connecting rod 26.
One difficulty observed with blade folding mechanism 10 is that the linkage experiences flight loads during rotor head operation. This results in the need to oversize the various components of the system to support the flight loads.
Therefore, it would be desirable to have a system in which the blade fold linkage is not in the flight load path.